(CNN) -- Venezuelan authorities have arrested a key ideological leader of the FARC leftist guerrilla group who is known as "The Singer" for his role as a musician promoting the rebel movement, officials said Wednesday.

"Today he is in custody and (Venezuelan) President (Hugo) Chavez has told us that he will be handed over to us," Colombian President Juan Manuel Santos said.

CNN affiliate Caracol TV reported that Torres, 57, became famous "because he always carried on his shoulder, next to his rifle, a guitar."

Several online video posts purport to show Torres, who is also known by the alias Julian Conrado, wearing military fatigues and cradling a guitar. In one, he sings about why he decided to become a guerrilla, and vows to continue fighting for the FARC "until death, for justice and peace, which is what I want."

Santos described Torres as a "narco-terrorist" when announcing the arrest Wednesday. The U.S. State Department had offered a $2.5 million reward for information leading to his capture, describing Torres as a leader who had helped set and implement cocaine policies for the guerrilla group.

Rebels from the left-wing Revolutionary Armed Forces of Colombia, commonly known as the FARC, have fought to overthrow the Colombian government for decades.

Authorities allege that Torres was a part of the inner circle of FARC leader Luis Edgar Devia Silva -- known as Raul Reyes -- who was killed in a 2008 raid in Ecuador.

Shortly after the raid, Colombian authorities announced that Torres had also been killed in the operation. They later retracted that statement, saying DNA tests showed that another man had been killed.

His arrest comes amid improving relations between the neighboring South American countries.

Tensions had flared between the two nations after Colombia accused Venezuela of harboring members of the FARC.

But shortly after his inauguration last year, Santos met with Chavez and pledged to wipe the slate clean.

In April Venezuelan authorities arrested Joaquin Perez Becerra, whom Colombian authorities accuse of conspiring in and helping finance terrorism through his alleged work as a spokesman for the FARC in Europe.

And in May Colombian authorities extradited to Venezuela Walid Makled Garcia, accused of being one of the world's top drug lords.